THIS invention relates to a method of processing value bearing material such as metal ores, and to an installation for carrying out the method.
According to the invention there is provided a method of processing heterogeneous value bearing material by pressure comminution, the method comprising compressing the value bearing material in a bed of particles, at low pressures and at low bulk material densities, thereby to liberate the value preferentially and to minimise size reduction of the material beyond the degree necessary for value liberation.
The particulate value bearing material is preferably subjected to a compressive bed pressure not exceeding 300 MPa, and more preferably not exceeding 50 MPa, or still more preferably, not exceeding 30 MPa.
Preferably, the bulk density of the particulate material bed is at least 20% lower than the density of the material making up the particulate.
The value bearing material may be subjected to a plurality of compression cycles.
The voidage of the particulate material bed (ie. the ratio of the bulk density of the particulate material bed to the density of the material making up the particulate) is preferably maintained by suitable intervention, such as a size classification stage, between at least some compression cycles.
The method may comprise compressing the value bearing material in an open circuit mode. By xe2x80x9copen circuit modexe2x80x9d is meant that the crushed material or part thereof is not recycled with feed material.
The method preferably results in desired proportions of a fine fraction enriched in a selected phase, mineral or metal and a coarse fraction depleted of said phase, mineral or value being produced, the fine fraction being separated from the coarse fraction for further processing of at least one of the fractions.
The coarse fraction may be discarded, or the crushing step may be repeated on the coarse faction, with the resulting crushed material being separated into a second coarse fraction and a second fine fraction, with a selected phase, mineral or value being recovered from the second fine fraction.
The separation of the coarse and fine fractions after crushing of the material is preferably carried out with a cut size calculated according to desired values of mass, value recovery and value grade in the coarse and fine fractions.
The heterogeneous value bearing material may be natural or synthetic, and will typically comprise metalliferous ore, a concentrate, a matte or a slag.
The heterogeneous material may be, for example, a base metal ore, gold ore, diamond ore, platinum ore, or titanium slag.
Further according to the invention there is provided an installation for processing heterogeneous value bearing material by pressure communication comprising:
at least a first crusher arranged to subject the value bearing material to one or more compression cycles in a bed of particles;
control means for adjusting the operation of the crusher so that the value bearing material is subjected to bed pressures not exceeding 300 MPa, in order to produce desired proportions of a value-enriched fine fraction and a value-depleted coarse fraction, thereby to liberate said value preferentially while minimising size reduction of the material beyond the degree necessary for value liberation; and
at least first separating means for separating the fine fraction from the coarse fraction of the crushed material.
The control means is preferably arranged to adjust the operation of the crusher so that the value bearing material is subjected to bed pressures not exceeding 50 MPa, and preferably not exceeding 30 MPa.
The separating means is preferably arranged to maintain a desired material bed voidage value so that the bulk density of the bed of particulate material is less than the density of the material making up the particulate.
The first device is preferably adjustable in accordance with the natural particle size of the value bearing compound or mineral within the heterogeneous material, thereby to minimise size reduction of the material beyond the degree necessary for value liberation.
The separating means for separating the fine fraction from the coarse fraction is preferably arranged such that the generation of ultrafines within the installation is minimised.
The installation may include at least a second crusher, the second crusher being arranged to be fed with the coarse fraction of the output of the first crusher; and at least second separating means for separating a fine fraction from a coarse fraction of the output of the second crusher.